Series fed log periodic antenna with coplanar conductor pairs



E, W. WOLOSZCZUK Jan. 12, 1965 SERIES FED LOG PERIODIC ANTENNA WITH COPLANAR CONDUCTOR PAIRS 3 Sheets-Sheet l Filed March 19, 1962 INVENTOR awm c WW ATTORNEYS Jan 12, 19.65 E. w. woLoszczuK 3,165,748

` SERIES FED LOG PERIODIC ANTENNA WITH COPLANAR CONDUCTOR PAIRS Filed MaICh 19, 1962 L( I 3 Sheets-Sheet 2 INVENTOR M BY /awmme ATToszNEY Jan- 12, 1965 E. w. woLoszczuK 3,155,748

SERIES FED LOG PERIODIC ANTENNA WITH COPLANAR CONDUCTOR PAIRS Filed March 19, 1962 3 Sheets-Sheet 3 A Paf P5] e/ F/G .4.

l l l Cs c4 C3/ C2/ 6C ace P5] P4, P3 ,D2/PM United States Patent O 3,165,748 SERIES FED LOG PERHDIC ANTENNA WETH COPLANAR CNDUCTR PAIRS Edmund Wergilinsz Woioszczuir, tllreimsiord, Essex, England, assigner to The Marconi Company Limited, a British company Filed Mar. I9, 1962, Ser. No. ltft Claims priority, application Great Britain, Mar. 29, 196i, MAW/6l 12 Claims. (Cl. 343-7925) This invention relates to directional aerial systems and has for its object to provide improved directional aerial systems of relatively cheap and simple construction suitable for use for high frequency communication and simil lar purposes and which can be constructed to be of large bandwidth, good impedance matching qualities and low side lobe level, i.e., such that the polar diagram of radiation exhibits only small side lobes adjacent the lobe corresponding to the main intended direction of radiation or reception. Aerial systems according -to this invention may be used equally well for transmission and reception.

According to this invention a directional aerial system comprises a plurality of conductor pairs of progressively dilfering lengths, the conductors of each pair being of substantially the same length, close together, and connected together at one end, and a plurality of series connecting substantially co-linear connectors of progressively different lengths and extending substantially at right angles to the conductors of the conductor pairs, each connector connecting the free end of one conductor of one pair to the free end of one conductor of the next pair, the ratio of the electrical length of each conductor pair to the electrical length of the connector connecting it to the next conductor pair of smaller length being substantially the same in all cases and the ratio of the electrical length of each conductor pair to that of the next conductor pair of smaller length being also substantially the same in all cases. The system is thus a series array and feeder means in association therewith are arranged at the end where the conductor pair of smallest length is situated. The various parts of the aerial system are so dimensioned that, at any particular given frequency within the intended working frequency range, one of the conductor pairs is electrically a quarter of a wavelength long and the connector connecting it to the adjacent smaller conductor pair is of an electrical length chosen to be at some value between one-twentieth and one-quarter of a wavelength. At this particular frequency this conductor pair will be the resonant part of the system.

In the case of a plane polarised aerial system in accordance with this invention all the conductor pairs are parallel to one another as well as being in parallel planes.

In one form of vertically polarised aerial system in accordance with this invention all the conductor pairs are vertical and substantially at right angles to the connectors which are in a line `arranged as close as practicable above the ground plane. In this embodiment unbalanced `feeder means is, of course,` provided. This embodiment has the advantage that it can be supported by a single relatively low mast-in practice of height only a little lowest intended working frequency of the aerial systemin conjunction withan inclined support wire from which the conductor pairs are supported. In embodiments, in which the connectors are close to the ground plane, it is sometimes convenient totconstitute them by the inner conductors of lengths of earthed screened cable. This has the advantage that radiation from the connectorsin any event very small when they are close to the ground* is reduced practically to zero. Radiation from connections between the conductors of the pairs at the ends more than aquarter of a wavelength at the id'dd Patented Jan. l2., 1965 ICC remote from the connectors is negligibly small because the conductors of each pair are close together.

Another form of plane polarised aerial system in accordance with this invention comprises two component aerial systems each in accordance with this invention, arranged with their connectors close together and all the pairs of conductors (of both component systems, that is) in a common plane so that one component system is arranged Ato be the mirror image of the other. In this type of embodiment, balanced feeder means is employed with the two wires oi a balanced feeder connected to the adjacent connectors at the smaller end of the whole system. Such abalanced aerial system will, of course, have a plane of polarisation dependent on the common plane oi the conductor pairs-vertical if the common plane is vertical and horizontal if the common plane is horizontal. However, the invention is not limited to plane polarised aerials. Thus circular polarisation can be obtained by employing two component aerial systems each in accordance with this invention and each having alternate conductor pairs at right angles to the` other pairs, arranged with their connectors close together so that corresponding alternate conductor pairs of both component systems are in `one common plane and the remaining conductor pairs are` in a second common plane at right angles to the rst. This embodiment is again a balanced system and is also employed in conjunction with a balanced feeder.

There may be employed in conjunction with any aerial system in accordance with this invention a director system of the Yagi type. Such a director system comprises parallel elements arranged in manner corresponding to that of the conductor pairs of the aerial system with which it is employed and extending from a backbone conductor substantially in line with the connectors of said aerial system. Where the said aerial system is unbalanced the director elements all extend parallel to one another on the same side of the backbone conductor, the said elements and the conductor pairs of the aerial system being in a common plane. Where the said aerial system is a plane polarised balanced system each director element is symmetrical with respect to the backbone conductor and again in a common plane with the conductor pairs of the aerial system. It is convenient and advantageous in such an arrangement to extend the backbone conductor with its extension lying midway between and parallel to the two lines of connectors of the two component aerial systems of the balanced system. Where the said aerial system is a circularly polarised balanced system each director element is symmetrical with respect to the backbone conductor and alternate director elements are in one plane and the remaining director elements are in a plane perpendicular thereto, alternate director elements which are co-planar with one another being also co-planar with alternate conductor pairs in the balanced circularly polarised balanced aerial system.

It will be appreciated that the net radiation from the connectors of a balanced aerial system in accordance with this invention is also only very small because the radiation from each length of connector is substantially cancelled out by that from a similar length of connector close and parallel thereto.

` The invention is illustrated in the accompanying diagrammatic drawings in which FIGURE 1 shows one embodiment which is of the unbalanced type; FIGURE la shows a detail modification of the embodiment of FIG- URE 1; FIGURE 2 shows, in conventional graphical manner, polar radiation diagrams obtainable from an aerial system as represented in FIGURE l; FIGURE 3 shows a system of the nature of that of FIGURE 1 with an associated director array of the Yagi type; FIGURE -4 shows a plane polarised balanced aerial system in accordance with the invention; FIGURE shows a system of the nature of that of FIGURE 4 with an associated Yagi-type director array; FIGURE 6 shows acircularly polarised balanced aerial system in accordance with the invention; and FIGURE 7 shows a system of the nature of that of FIGURE 6 employed with an associated Yagitype director array. Like references denote like parts throughout. n

Referring to FIGURE l, the aerial system therein shown comprises a plurality of (in the particular case illustrated eleven) conductor pairs referenced Pl to PII inclusive each consisting of `two conductors referenced I and 2 in all cases. These conductors are all vertical and the conductors of each pair are connected together at their upper ends by connections which are very short since the said conductors of each pair are close together. The conductor pairs are connected together in series to form a series array by co-linear conductors referenced C2 to CII inclusive. The ratio of the electrical length (height) of each conductor pair to the electrical length of the connector connecting it to the next, smaller, conductor pair is constant throughout the system and the electrical lengths of the conductor pairs increase logarithmically from the shortest pair P1 to the longest pair P11. Thus if H1, H2, H3 H11 are the electrical lengths of the conductor pairs P1, P2 Pil respectively, then and so on, where k is a constant. The reciprocal of k, i.e., 1/ k may be referred 4to as the taper of the system. The co-linear connectors C2 to CII are close to the ground plane G so that radiation therefrom is very small. There will also be negligible small radiation from the horizontal connections between the conductors of each pair, since these connections are of negligible length. A feeder shown as a screened cable F is connected to the system at the smaller end.

At any frequency within the working range of the system there with be some part thereof which is resonant, the resonant conductor pair being that pair which has an electrical length of a quarter of a wavelength at the particular frequency considered. The resonant pair is spaced from the next smaller pair by a distance which is from 1/0 to 1A of a wavelength at the frequency considered, the optimum distance depending on the taper, the value of which determines the gain of the array. |The limits of bandwidth of the system are set by the dimensions of the longest and shortest conductor pairs and it is possible to design a single aerial system to cover the whole high frequency band.

As will be seen the aerial system is not only structurally simple in itself, but it can be supported by a single mast which need only be a little over a quarter of a wavelength high at the lowest frequecny in the band for which the system is designed. Such a mast is represented in FIG- URE 1 by the broken line M, the conductor pairs being supported as conventionally indicated from a stay or guy S leading down at an angle from the top of the mast.

The connectors C2 to CII inclusive may be and prefer-l ably are constituted by short lengths of screened co-axial cable. This is illustrated in FIGURE la which shows a modification of this nature, the said ligure showing this modification (to a larger scale) for the ringed round portion of FIGURE l.

FIGURE 2 shows in conventional manner horizontal and vertical polar radiation diagrams which have been obtained from an experimental system as shown in FIG- URE l. In FIGURE 2, the full line curve HPD is the horizontal plane polar diagram and the chain line curve VPD is the vertical plane polar radiation diagram in the direction X which corresponds to the direction X of maximum radiation-endwise-shown in FIGURE l.

FIGURE 3 shows an arrangement of the nature of that of FIGURE 1 combined with a Yagi-type director consisting of vertical director elements D. These elements hl may be regarded as extending from a backbone conductor, although in fact, in FIGURE 3 because the elements D are vertical, there is no separately provided backbone conductor, the ground plane itself serving as the backbone conductor.

FIGURES l and la show unbalanced systems with associated unbalanced feeders. FIGURE 4 shows a balanced system. As will be seen, it consists in effect of two component systems, each of the general nature of that of FIGURE l in mirror image arrangement with the connectors close together and parallel. In FIGURE 4 references corresponding to those used in FIGURE 1 are applied to one component system and similar but primed references are applied to the other component system.

This balanced system is, of course, associated with a balanced line feeder (not shown) connected at the terminals i FIGURE 5 is largely self-explanatory. It shows an aerial system of the nature of that illustrated by FIGURE 4 used as a launcher in association with a Yagi director system Vcomprising director elements D extending from a backbone conductor referenced BC. In FIGURE 5 there is an extension BCE of the backbone conductor back between the connectors of the launching aerial system. This back-extension is, of course, not necessary, but its provision is preferred.

If the conductor pairs and director elements of FIG- URE-3 4 and 5 are vertical, the systems shown by those figures will be vertically plane polarised. If they are horizontal, the systems in question will be horizontally plane polarised.

FIGURE 6 shows another balanced aerial system which is, however, circularly polarised. The system of FIG- URE 6 differs from that of FIGURE 4 in that all the conductor pairs are not co-planar but alternate pairs are in one plane and the remaining pairs in a second plane perpendicular to the first. As shown in FIGURE 6 the odd numbered pairs PI, PI; P3, P3 P13, P13 are in a vertical plane and the even numbered pairs P2, P2', P4, P4 Pll21, P12" are in a horizontal plane. The even numbered pairs look inclined in FIGURE 6, but this is only in order to represent, in perspective manner, that the even numbered pairs are as stated, at right angles to the odd numbered pairs. All the conductor pairs are at right angles to the line of the substantially co-linear connectors which are, of course, crossed over between the pairs PI, PI and P2, P2', the pairs P3, P3 and P4, P4 PII, Pill. and P12, P12 as indicated.

FIGURE 7 shows a system of the nature of that of FIGURE 6 employed with a Yagi director arrangement. FIGURE 7 is largely self-explanatory. As will be seen, the Yagi comprises a backbone conductor BC substantially co-linear with the line of connectors of the launching aerial system and director elements DE and DO, of which the alternate elements DE are vertical and the remaining elements DO are horizontal.

I claim:

l. A series array directional aerial system comprising a plurality of conductor pairs of progressively differing lengths, the conductors of each pair being of substantially the same length, close together, and connected together at one end, and a plurality of series connecting substantially co-linear connectors of progressively different lengths and extending substantially at right angles to the conductors of the conductor pairs, each connector connecting the free end of one conductor of one pair to the free end of one conductor of the next pair, the ratio of the electrical length of each conductor pair to the electrical length of the connector connecting it to the next conductor pair of smaller length being substantially the same in all cases and the ratio of the electrical length of each conductor pair to that of the next conductor pair of smaller length being also substantially the same in all cases.

2. An aerial system as claimed in claim 1 wherein the parts of said aerial system are so dimensioned that, at a selected frequency within the intended Working frequency range, one of the conductor pairs is electrically a quarter of a wavelength long and the connector connecting said one conductor pair to the adjacent smaller conductor pair is of an electrical length of between one twentieth and one quarter of a wavelength.

3. A plane polarised aerial system in accordance with Claim 1 wherein all the conductor pairs are parallel to one another as Well as being in parallel planes.

4. A vertically polarised aerial system in accordance with claim 1 wherein all the conductor pairs are vertical and substantially at right angles to the connectors which are in a line above and close to the ground plane.

5. An aerial system as claimed in claim 4 wherein the connectors are constituted by the inner conductors of lengths of earthed screened cable.

6. A balanced plane polarised aerial system comprising two component aerial systems each as claimed in claim 1 arranged with their connectors close together and all the pairs of conductors of both component systems in a common plane, one component system being the mirror image of the other.

7. A balanced circularly polarised aerial system coniprising two component aerial systems each as claimed in claim 1 and each having alternate conductor pairs at right angles to the other pairs, the connectors between alternate conductor pairs and the connectors between the other pairs being close together, so that corresponding alternate conductor pairs of both component systems are in one common plane and the remaining conductor pairs are in a second common plane at right angles to the said one common plane.

8. In combination with an 'aerial system as claimed in claim 1, a director system of the Yagi type comprising parallel director elements arranged in a manner corresponding to that of the conductor pairs of said aerial system and extending from a backbone conductor substantially in line with the connectors of said aerial system.

9. A combination as claimed in claim 8 wherein the aerial system is unbalanced and the director elements all extend parallel to one another on the same side of the backbone conductor, the said elements and the conductor pairs of the aerial system being in a common plane.

10. In combination with a balanced plane polarised aerial system as claimed in claim 6, a director system of the Yagi type comprising parallel director elements arranged in a manner corresponding to that of the conductor pairs of said aerial systems and extending from a backbone conductor substantially in line with the connectors of said aerial systems, each director element being symmetrical with respect to the backbone conductor and being in a common plane with the conductor pairs of the aerial systems.

11. A combination as claimed in claim 10 wherein the backbone conductor has an extension lying midway between and parallel to the two lines of connectors of the two component aerial systems of the balanced system.

12. In combination with a balanced circularly polarised aerial system as claimed in claim 7, a director system of the Yagi type comprising parallel director elements arranged in a manner corresponding to that of the conductor pairs of said aerial systems and extending from a backbone conductor substantially in line with the connectors of said aerial systems, each director element being symmetrical with respect to the backbone conductor, alternate director elements being in one plane and the remaining director elements in a plane perpendicular thereto, the alternate director elements which are co-planar with one another also being co-planar with alternate conductor pairs in the balanced circularly polarised aerial system.

References Cited by the Examiner UNITED STATES PATENTS 3/40 Katzin 343-908 4/63 Greenberg 343-908 OTHER REFERENCES HERMAN KARL SAALBACH, Primary Examiner. 

1. A SERIES ARRAY DIRECTIONAL AERIAL SYSTEM COMPRISING A PLURALITY OF CONDUCTOR PAIRS OF PROGRESSIVELY DIFFERING LENGTHS, THE CONDUCTORS OF EACH PAIR BEING OF SUBSTANTIALLY THE SAME LENGTH, CLOSE TOGETHER, AND CONNECTED TOGETHER AT ONE END, AND A PLURALITY OF SERIES CONNECTING SUBSTANTIALLY CO-LINEAR CONNECTORS OF PROGRESSIVELY DIFFERENT LENGTHS AND EXTENDING SUBSTANTIALLY AT RIGHT ANGLES TO THE CONDUCTORS OF THE CONDUCTOR PAIRS, EACH CONNECTOR CONNECTING THE FREE END OF ONE CONDUCTOR OF ONE PAIR TO THE FREE END OF SAID CONDUCTOR OF THE NEXT PAIR, THE RATIO OF THE ELECTRICAL LENGTH OF EACH CONDUCTOR PAIR TO THE ELECTRICAL LENGTH OF THE CONNECTOR CONNECTING IT TO THE NEXT CONDUCTOR PAIR OF SMALLER LENGTH BEING SUBSTANTIALLY THE SAME IN ALL CASES AND THE RATIO OF THE ELECTRICAL LENGTH OF EACH CONDUCTOR PAIR TO THAT OF THE NEXT CONDUCTOR PAIR OF SMALLER LENGTH BEING ALSO SUBSTANTIALLY THE SAME IN ALL CASES. 